It has long been a common practice to start standby power generators using the energy stored in batteries to drive starter motors, which in turn crank the generator until the generator starts. However, the load placed upon the batteries reduces the life of service of the batteries significantly. A typical battery for starting a standby power generator may only have a useful life of about three years. In addition, the energy output of even a good battery may be severely reduced when used under extreme temperature conditions.
Advances have been made in technology regarding capacitors, which are capable of storing electrical energy, but until recently were not capable of storing the amounts of energy needed to start a generator. However, large capacitance capacitors, for example electric double layer capacitors, have been developed which are capable of storing large amounts of electrical energy. These capacitors are sometimes known as super capacitors, and are finding use in applications such as in engine starting circuits.
For example, in U.S. Pat. No. 5,157,267, Shirata et al. (Shirata) disclose an apparatus for starting an engine which uses a capacitor in parallel with a starting battery. The battery charges the capacitor through a boost controller, i.e., a DC to DC inverter, to a voltage slightly higher than the battery voltage. For example, for a battery voltage of 12 volts, the capacitor would be charged to 14 volts. The energy stored in the capacitor is then used to start the engine, as the battery continues to charge the capacitor during the start cycle.
Although the apparatus of Shirata uses a capacitor to start an engine, the battery must still continue to work under load to maintain a charge on the capacitor. Therefore, the battery must still be subjected to the stresses of continual quick-draining charge-discharge cycles, thus shortening the useful life of the battery. It would be desirable to provide a starting system for a standby power generator which did not subject the battery to constant discharging and charging during the starting process.
The present invention is directed to overcoming one or more of the problems as set forth above.